Existing road-portable, or towable, commercial material screening equipment generally is either of one or two distinct designs or configurations. Each design and configuration includes a frame and one or more, typically a pair, of sloping, vibratory shaker surfaces supported within the frame. The frame has a tall end and a short end, joined by two sides, and has funneling surfaces on the sides inwardly directed to funnel feed material to a shaker head with a screen surface to separate soil or other waste material. The material to be screened is dumped onto the upper surface, such as by a payloader, and the larger material falls from the short end of the primary screening surface; while material which is smaller than the primary surface passes through the surface to a lower separating surface, with dimensions to permit coarser material to be discharged from the one short end of the frame, and finer material to fall to an open space within the frame or onto a conveyor belt for retrieval from the open space.
The first and most common soil separating apparatus has a primary surface composed of woven wire, for example, a woven wire or perforated flat surface. Such vibratory separating material apparatus, are described, for example, in U.S. Pat. Nos. 4,197,194, 4,237,000 and 4,256,572, and U.S. Pat. No. 065,263,836, all hereby incorporated by reference. These apparatus are known in the industry as Screen-All.RTM. soil separators (Screen-All is a registered trademark of James L. Read of Middleboro, Mass.).
A second material separating design is not as widely employed, but is desirable in many special applications, such as in separation of soil compacted with or without waste, or with a wide variety of combinations of different types of materials. The second apparatus is useful due to its high level of effectiveness with other materials problems. The second separating material apparatus is designed with a plurality of vibrating fingers or elongated rods as the primary upper separating surface. Cylindrical rods or fingers are mounted as combs in planar rows, which overlap to form separate tiers or decks and are fit into shaker mechanisms or apparatus in a downwardly inclined arrangement. The plurality of combs are designed to form a pattern of staggered layers that breaks up the unscreened material that rolls upon it, and breaks up the material as it passes from the tall to the short end of the frame. This second type of waste material separating apparatus is described, for example, in U.S. Pat. No. 5,219,078 issued Jun. 15, 1993 and U.S. Pat. No. 5,322,170, issued Jun. 21, 1994, both hereby incorporated by reference.
The existing screening equipment, with either the first or second designed shaker heads or even combination shaker heads, do not have capacity to be interchangeable. A significant need does exist in the industry, however, for interchangeable shaker heads; that is, interchangeable upper separating surfaces. There have been efforts to provide add-on screening apparatus, which attempt to offer the benefits of either woven wire or rod-finger upper screening surfaces. These existing add-on separating apparatus, in order to function, actually lessen the overall performance and longevity of the originally designed vibratory separating apparatus. For example, such add-ons increase the overall height of the existing apparatus, and therefore create problems for the discharge of material by a backhoe or payloader onto the add-on upper separating surface. Further, in order to obtain a single soil separating apparatus machine for convertibility of the upper material screening separation, the overall effectiveness of the apparatus is compromised.
Thus, it is desired to provide an improved waste material vibratory separating apparatus with a universal shaker head with means to provide for interchangeable screening surfaces on its primary upper surface, that is easy to change and does not compromise the height or effectiveness of the screen apparatus in use.